Single-leg training is all the rage in the fitness industry. It seems as though everyone is touting its unilateral praises.

The worst of the worst are the clowns who act like they've been on the singe-leg bandwagon since Jimmy Carter carried his own golf clubs. They boast and brag about how long it's been since they or their athletes have done a bilateral exercise like somehow it's a testament to their skill as coaches.

Let's get biases out of the way up front. I like single-leg training. I think it can benefit athletes and lifters of all shapes and sizes.

Baseball player? Yep.

Distance runner? Sure.

Elite-level powerlifter? Absolutely.

I even created the Single-Leg Solution DVD and manual to explain all the ins and outs of single-leg training. So I'm hardly a single-leg hater. Instead, let's focus on the biggest reason that single-leg training can help you achieve your goals, whether they're strength or physique focused.

It all comes down to stability.

Squats or Leg Presses?

How many reading this can squat more than you can leg press?

Even if you can squat 600 pounds for breakfast, I'll bet you can lie down on any leg press machine in the world and probably move several hundred pounds more than that.

The reason is stability, and lots of it.

In a free squat exercise (front, back, basically anything other than a Smith machine), your body is required to develop a tremendous amount of internal stability.

Your hips are trying to control your knees so they don't cave in. Your core and torso are working tremendously hard to keep your chest up and your back flat. You're using a ton of muscle just to stabilize and support the weight, let alone move it up and down!

In contrast, on a leg press you have a ton of built-in, external stability.

You have a built-in core, as your entire lower back is supported. You don't even need to use your torso as much because it's not supporting the weight to the same degree as you would in a squat.

The sled also minimizes hip and knee stability, as all you have to do is hop in and push the weight up and down.

So this is a great lesson in stability – the more external stability you have, the more prime mover activation you can achieve.

Less Stability

More Stability

More Stabilizer Activity

Less Stabilizer Activity

Less Prime Mover Activation

More Prime Mover Activation

In contrast, the less external stability you have, or the more unstable you are, the more stabilizer activity you elicit as your body is just trying to keep you upright.

Bilateral or Unilateral?

Now, let's take this example and apply it to bilateral versus unilateral lifts.

Stability demands are obviously in play in a squat, which we've discussed. But in any lift, you have what's called a base of support (BOS). A general definition for BOS is the area underneath and between both feet.

Think about multi-ply powerlifting for a moment. These guys are masters of efficiency and gear use. How do they squat?

They go extra wide, not only to maximize the gear use, but to give them a tremendous base of support. This is important if you want to handle maximal weights because a wider BOS means more stability and more stability means more prime mover activation.

Now, let's take that wide base of support and move it in; and not just a little like a narrow squat, but a step further into a split-stance position like a lunge.

Notice that your base of support just got a hell of a lot smaller?

Small BOS

Large BOS

Single-Leg Exercise

Split-Stance Exercise

Traditional Squat

Powerlifting Squat

And that's just a split-stance exercise! Think about how small your BOS is when you perform true single-leg work like single-leg RDL's, step-ups, or single-leg squats?

As you can see, it's a tradeoff. The more stable you are, the more prime mover activation you get, and the less stable you are, the more stabilizer activation you get.

Which leads me to my main point for this entire article:

Why use so much damn weight on single-leg exercises?

I'm not talking about using baby weights. What I'm saying is that if you're doing single-leg work with a ton of weight, falling all over the place, and making yourself look like an idiot, you need to check your ego at the door and do it right.

You wouldn't put one plate on each side of the leg press to get more stabilizer activity. If you did, you'd be using the wrong tool for the wrong job. If you're going to leg press, the goal is to go heavy and build some steel wheels.

The goal of single-leg and split-stance training is to improve your stability so that when you go back to your bilateral lifts, you're inherently more stable and can use more weight!

You don't have to use 10-pound dumbbells, but you just might, if that's what it takes to stay stable and build some internal stability.

The Powerlifting Example

I've been lucky in that over the past year I've done a lot of work with the guys over at Elite. Needless to say, these are some of the strongest humans in the world (if you can consider anyone who squats a grand a human) and it's an honor to work with them.

When I evaluate many of them, it's crazy. Obviously they're big and stiff, which allows them to move a ton of weight, but these guys are incredibly "stuck" in their gear. Even when they don't have gear on, it looks like they have gear on.

Their hips are abducted and externally rotated, their hip internal rotation is shot, and due to all their time in a wide-stance and in gear, their hip stability is really bad.

This is a difficult idea for some to get their head around. How can a guy that big be unstable?

Just because you're strong doesn't mean you're inherently stable, especially if you're getting much of your stability from supportive gear and manipulating biomechanics.

One of the first things I do with these guys is to get them on a regular soft-tissue and mobility routine, just to get them some basic movement capacity. And if they're in the off-season, I absolutely get them doing some single-leg work, even if it's only one or two exercises per week.

The results speak for themselves. These guys often report feeling "healthier" and having fewer aches and pains while also hitting PR's in their following meet.

I didn't do anything to improve their strength, like write up a circa max or block periodization program for their squat. Instead, I gave them more internal stability, so that when they go wide and throw the gear back on, their prime movers can engage even harder than before.

It's like taking a Ferrari and giving it the ultimate tune-up. A super powerful sports car just got even more awesome!

But which one is better?

Are split-squats and single-leg work better?

Shouldn't we just be squatting heavy?

Can I do leg presses instead of squats?

It's like asking which is better between a hammer, a wrench, and a screwdriver. They're all important, and each one has value in certain situations. All it really comes down to is your needs and goals. The more external stability you have, the more prime mover activation you can get.

Want to know why some bodybuilders spend so much time on machines? Because they don't give a rat's ass about being functional. It's about building a muscular physique. And machine-based training is a surefire way to build your prime movers to a high degree.

Powerlifters, Olympic lifters, and athletes squat because they get a strong carryover to their sports. There's no better way to get strong than heavy squats and deadlifts.

Single-leg work absolutely plays a role as well. I don't think you're going to become a monster by focusing solely on your step-up and split-squat for the next 10 years, but you can definitely improve your stability and performance by incorporating them into your program.

I'm over debating which one is "superior." I really don't care. You're free to do and train however you want. If something helps you achieve your goals, good for you. The goal (at least for me and my athletes) is simple: To be able to train hard and stay healthy, for as long as possible.

And I'm Out

My hope is after reading this mini-rant/diatribe that you have a better understanding of how single-leg training can improve your physique and performance.

In the end, the goal is to maximize stability so when you go back to the heavy bilateral stuff, you're going heavier than before and achieving new PR's. It may not be the Holy Grail of training technique, but intelligent use of single-leg work can absolutely take your strength and physique to the next level.